Too often tradition drives design, and golf is an ancient sport. When golf was invented some 500 years ago, a simple stick was state-of-the-art. Featured today, and for all practical purposes unchanged for half a millennia, the maximum diameter of the handle end of a typical golf club shaft is about half an inch. This small diameter may be necessary with full-swing clubs, because of the different functions of the left and right hands—the lower hand finger grip must roll the club over near impact while the upper hand balances the club under the heel pad of the palm. However, because the hands perform similar functions in a putting stroke, this small diameter grip is unnecessary.
In fact, the full swing and putting stroke are entirely different. In a full swing, the golfer's feet, legs, hips, and shoulders are in motion: the body dominates the swing. Conversely, during a preferred putting stroke, the club dominates the stroke. The body remains nearly motionless, with the arms acting as an extension of the club to form a simple pendulum. Full-swing clubs may be swung at speeds of one hundred miles an hour or more, driving the recent emphasis on lightweight materials such as graphite and titanium. Compared to these clubs, the putter carries out its function at a near stand-still, and such a primary emphasis on lightweight design would be misplaced. In short, putters perform a very different function than the other thirteen full-swing clubs, yet the design of putters—especially their grips—is in many ways the same.
Control and accuracy are possibly more important in putting than in any other aspect of the golf game. No longer is the golfer's target a fairly large area in the fairway, perhaps several hundred yards away, or even the somewhat smaller area defined by the green. Rather the target is the tiny cup into which the golfer must roll the ball. The golfer must strike the ball along a precise line with a precise speed, taking into account both the contour and texture of the green's surface, in order to sink a putt. Unfortunately, with a typical prior art putter, there are many forces acting on the putter in several different directions during the putting stroke. Hence, it is the golfer's job to counteract these forces such that the sum of the magnitudes and directions of all the various forces involved results in the putter's applying exactly the right amount of force in exactly the right direction. This is no easy task. But the task can be simplified by minimizing the effect of an imperfect putting stroke, and reducing the number of dissonant forces the golfer must counteract in order to strike the ball with the requisite force and direction.
An imperfect putting stroke may result in the club head (or blade) being struck off-center, which may cause the putter to twist in the golfer's hands and lose the all-important line. A club's resistance to this twisting is a function of the club's moment of inertia. More specifically, the moment of inertia of a golf club affects the club's resistance to rotating about an axis defined by its shaft when the golf ball is struck away from the center of percussion (or sweet spot) of the club head. An increase in the magnitude of the moment of inertia of a golf club, and particularly the putter, is a desirable object of golf club design. This object has been recognized, as designs incorporating heel-toe weighting in the club head to increase the moment of inertia of the club account for approximately eighty percent of putters on the market today, according to a recent survey. Many of these designs use sophisticated and complex heel-toe or perimeter weighting systems and exotic and extremely heavy materials such as tungsten or special alloys. While they have increased the moment of inertia somewhat, it would be most desirable to increase the moment of inertia by an order of magnitude or more.
Another important design parameter, one which affects the feel and balance of the putter in the golfer's hands as it is positioned behind the golf ball and moved through the putting stroke, is the location of the entire putter's center of gravity, as opposed to the center of gravity of just the blade. Prior art designs have added weight to various places in the club, to alter the location of the center of gravity. A typical design adds a relatively small amount of weight, as compared to the overall weight of the golf club, within the club shaft at the handle end of the club. The added weight moves the center of gravity up the club shaft towards the grip end of the club marginally, but to the inventor's knowledge no design that adds weight exclusively within the inside of a standard diameter club shaft can move the center of gravity of the putter so far as to locate it actually in the region of the club gripped by a golfer, while maintaining a conventional length club.
Consequently, the center of gravity of the whole club in a typical prior art putter is generally located in the shaft somewhere between six inches or more below the lower end of the grip and a few inches above the head. As the golfer grips the club, the hands form a pivot and, because the center of gravity of the club is some distance from the hands, the shaft serves as a torque arm. The club itself thus exerts a torque or pull on the hands that is a product of the mass of the club (directed through the center of gravity) and the length of this torque arm. As a result, the club feels “bottom heavy.” The relatively light weight of a typical club head (eight ounces or so) would seem to be a small input into the function of the swing. However, in a prior art putter the club head accounts for at least half of the weight of the whole club, and the club head's weight is multiplied over the long lever arm from the grip to the center of gravity. Consequently, the club head's weight causes a large, hard to control, output during the swing. Moreover, because each of the golfer's hands is a different distance from the center of gravity of the club, the golfer must apply different forces with each hand to maintain the club's position. To make matters worse, the bottom-heaviness of a typical putter exerts a torque on the golfer's hands during the stroke. This torque is a function of the angle of the club from vertical, so that as the club moves through the putting stroke the torque is constantly changing. Then one must add into the equation the vacillations and fluctuations of the average golfer as he attempts to balance this constantly changing force applied differently to each hand, possibly under the intense pressure of a golf game.
These problems with the bottom-heavy design may be explained in terms of equilibrium. An object is in equilibrium when the sum of the forces acting upon it is zero. Further, an object may be in unstable equilibrium or in neutral equilibrium. When an object is in unstable equilibrium, any displacement away from its equilibrium position will cause the object to tend further away from equilibrium. If in the physical system of a golfer gripping a putter, the fulcrum is taken to be the normal pivot at the golfer's hands on the handle, a typical prior art putter is in unstable equilibrium. Thus the inherent difficulties described above.
When an object is in neutral equilibrium, on the other hand, any displacement of the object away from a first equilibrium position will result in the object's being in equilibrium at its new position. In other words, when one moves an object in neutral equilibrium from a first position to a second position, the object tends to stay in the second position. A golf putter in neutral equilibrium would be advantageous to the golfer because it would minimize, or possibly even eliminate, many of the varying forces that the golfer must otherwise counteract.
In addition to its instability and relatively small moment of inertia, the small diameter grip of a typical prior art putter tends to place the control of the putting stroke in the small, twitchy muscles of the hands and forearms. The small diameter grip promotes much more of a finger grip, rather than a preferred palm grip for putting, which may result in the golfer clenching the club with the fingers and placing a heavy load on the small finger muscles. This small grip, in conjunction with the bottom heaviness of the traditional design, requires the golfer to apply force with the smaller, twitchy, and unreliable muscles of the wrists and forearms to counteract the dissonant forces described above, even as the golfer addresses the ball prior to beginning the putting stroke.
Another problem caused by the bottom-heavy design of most prior art putters is that as the putter is swung back, the handle end tends to move ahead of the club head. Given the linear, rigid characteristics of a typical putter, and its concentration of weight toward the club head, as the putter is pulled by its lighter end (the handle end), the greater inertia of the club head requires a greater force to move it from its resting position, thus creating a tendency for the handle to move first. This non-uniform movement causes the imaginary line formed by shaft up through the arms to the shoulders to be broken at the hands during the swing, effecting a chaotic double pendulum. The problem is exacerbated by the fact that the pendulum's bob is the putter's head. This double-pendulum effect is undesirable in light of the commonly preferred method of swinging a putter, which is to pivot only at the shoulders, keeping the wrists locked, thus simulating a simple single-pendulum swing.
Moreover, the typically circular cross-section of most prior art grip designs does not assist the golfer in hand placement. A circular grip feels the same no matter which way it is held; the golfer must rely on visual cues to properly grasp and align the club.
Ergonomics may be defined as the relationship of man to machine. Simply put, each of the preceding characteristics of conventional putter design impairs the overall ergonomics of the club. A more ergonomic design is needed.
Finally, many commercially successful putters have complex and sophisticated heel-toe or perimeter-weighting systems and use exotic materials. These exotic materials, such as elastomer, tungsten or special alloys, and the materials science research involved in developing them, make putters expensive. In addition, complex designs may require special manufacturing processes, driving up costs even more.
Hence, there exists a need for a golf putter with a high moment of inertia; that does not have a bottom-heavy feel; that maintains its equilibrium throughout the putting stroke; that does not primarily engage the small, twitchy muscles of the hands and forearms; that has a grip shape which promotes proper hand placement; that increases the overall ergonomics of the club; and that is simple and inexpensive to manufacture.